Current treatments for AIDS use drugs; such as azidothymidine (AZT), and other protease inhibitors which inhibit HIV replication. These treatments have only limited efficacy because HIV mutates rapidly and new strains that are drug-resistant eventually develop.
The use of photochemical inactivation procedures are currently used to render blood safe for transfusion. For example, the addition of phthalocyanines such as Pc4 to blood followed by exposure to red light has been shown to effectively reduce viral load in vitro (Margolis-Nunno, H., et al. Transfusion 36:743-750 (1996)). Pc4 kills HIV by binding to the viral envelope and producing reacting oxygen species (ROS) upon light activation, which subsequently cause damage to the viral proteins, rendering the virus non-infectious. Because binding of Pc4 to viral membrane is nonspecific, drug-resistant strains cannot arise from this treatment.
Accordingly, if such treatment could be performed on AIDS patients to reduce HIV viremia in their blood, such treatment is expected to be beneficial since a reduced quantity of HIV in plasma is a predictor for enhanced survival of AIDS patients (Mellors, J. W., et al. Science 272:1167-1170 (1996)). However, because photo-inactivation is not specific, Pc4 and other photosensitizers, can also bind to red blood cell (RBC) membranes and cause RBC damage. Accordingly, there exists a need for rendering RBC safe while at the same time maintaining good viral kill in vivo.
The present invention is directed to a method for treating a viral infection, such as HIV, in a subject in need of such treatment, which utilizes photochemical inactivation procedures to reduce the level of infectious virus contained in the blood while simultaneously minimizing the damage done to red blood cells. In this connection, the inventor has found that by incorporating the photosensitizer in a liposome formulation and applying light at a certain wavelength above the maximum absorption of the photosensitizer, a good virus kill can be achieved while minimizing the damage to red blood cells.
In addition, the inventor believes that by incorporating the photosensitizer in a liposome formulation and also administering a quencher alone or in a liposome formulation, the damage to red blood cells also can be minimized.